The idea of Y chromosome haplogroups changing is pretty confusing. The R1b haplogroup is the most common in Europe. R1b1 and R1b2 both descend from R1b but R1b1a only descends from R1b1. Haplogroup labels (like R1b1a1a2b often get relabeled as new mutations (SNPs ) near the root of the haplogroup tree are found and so those labels changed. People who were R1b1 may for a period of time have been labeled R1b2.
Because of the many changes, a new naming system was adopted. Some males in the major "I" haplogroup became I-Z59 (The letter "I" followed by the name of the most recently occurring SNP that male is known to have on his Y). He (and all his direct male line descendants) will ALWAYS belong to the I-Z59 haplogroup. That will never change. However as more of his Y chromsome is explored (with tests such as "Big Y") it will be determined that some SNPs have happened more recently. Say 20 generations ago, or even 9 generations ago. Y haplogroups have their own ancestral tree and descendant chart. The sons of some men living today have a SNP on their Y chromosome that their father does not. One of those SNPs might be called "F238" So the father is I-Z59 and the son is I-F238, But the son will also always belong to the I-Z59 haplogroup.
For now continue to use haploTYPES (e.g. the 37 STR markers reported in a Y-DNA37 test). They are still much easier to use for ancestry within the last 2,000 years.